Electric discharge tube



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WlLHELMUS ANTONIUS ROOVERS INVENTOR mfi AGENT Patented Nov. 23, 1948 ELECTRIC DIS CHARGE TUBEi WilhelmusAntonius.Roovers,EindhovemNetherlands, assignor to Hartford'Nati'onal Bank and; Trust Company, Hartford; Cnn., as. trustee Application November 22, 1941i,v Serial No; 711,657 In the Netherlands October 12, 1945,

Section 1,. Public Law 690, August 8, 1946 Patent expires October 12, 1965 4 Claims. 1.

This invention relates to electric discharge tubes, the bulb of which is sealed by m'eansof a glass bottom which comprises the contact studs and in which an exhaust tube is provided, and more particularly to the construction of the exhaust tube.

In tubes having a metal bottom plate it was known to use a metal exhaust tube to constitute the centreing stud. For this urpose this exhaust tube was arranged eccentrically, so that it could also serve as a location member. This has, hoW- ever, the drawback that both the centreing and location are difiicult.

Otherwise, the attachment of a metal exhaust tube to a metal tube bottom entails little difficulty, whilst a very strong, construction can be ensured. The matter is entirely diiferent, however, if the bottom plate is made from glass. Since a centreing stud, particularly if it serves at the same time as a location lug, may be subjected to heavy forces on introducing the tube into the holder, the use of a metal exhaust tube as a centrein stud in combination with a glass bottom was considered to be unsuitable. Hence if, for some reason or other, a metal exhaust tube was sealed into a glass bottom plate, this tube was always surrounded by a protecting bush which could be shaped into the form of a centreing stud and location device. Furthermore it has been proposed to use a glass exhaust tube at the same time as a centreing stud and location lug. If, in this case, an exhaust tube having the usual Wall thickness was used, a breakdown of the exhaust tube is liable to occur, whereas on using an exhaust tube having a larger wall thickness, the sealing. islikely to involve great internal stresses in the glass which may cause cracking. Therefore this construction has been abandoned.

However, the use of a glass bottom plate has many advantages with regard tov a simple manufacture, the capacity between the supply conductors and the length of the leakage paths. Also in the case of very short waves the use of a glass bottom is desirable.

The aforesaid well-known form of construction, in which a separate protecting bush was used as a centreing stud, has a limitation, however, in that it is rather cumbersome, particularly with regard to the attachment of such a bush to the bottom of the tube. This construction, moreover, occupies comparatively much space, so that it could not be used for small-sized tubes, and the exhaust tube was again provided at the top.

The said disadvantages ar obviated by providing that in an electric discharge tube, the bulb of which issealed by means of a glassbottom, into which contact members and a central metal exhaust tube are sealed, the exhaust tube is, according to the invention, shaped into the form of a centreing stud and a location member and serves at the same time for holding the tube in the holder.

It has been found that, particularly-in the case of tubes having a small diameter, the construction according to they invention is sufficiently strong, so that the arrangement of the exhaust tube at the upper end of the tube is not necessary;

Furthermore it is of' importance that the exhaust tube is made from a metal or a metal alloy, the coefficient of, expansion of which is adapted to that of the glass, in order to avoid as much as possible the occurrence of internal stresses. A very suitable combination is obtained, if an exhaust tube of ferrochromium is sealed into a bottom of pressed glass substantially having the following composition: SiOz 51%; PbO; 32.2%; CaO 2%; K20 13.3%; NazO 1.5%. In order to reduce the: cost it is possible to make only that part of the exhaust tube, which has to be sealed in, from ferrochromium and the centreing body proper, which comprises the location lug, from iron, for example. This permits th centreing body to be soldered, preferably by means of copper, to the sealed ferrochromium part. in a vacuum-tight manner.

Larger differences between the coefficients of expansion of glass and metal are. permissible if the glass of the bottom plate has such a structure that it consists of from 5 to 10% of scattered cavities. In this case, it is even not impossibl to make the whole of the exhaust tube from iron and to seal it into the aforesaid kind of glass.

In order that the invention may be clearly understood and. readily carried into efiect, it will now be described more fully with reference to the accompanying drawing, given by way of example, in which Figs. 1 and 2 represent forms of construction of an exhaust tube according to the invention.

In Fig. 1 the reference numeral l designates the bulb of a discharge tube which, in the present case, is made from glass, but may also be made of metal and which is sealed by means of a glass bottom plate 2. Into this bottom plate 2 are sealed the contact members 3 and a tubule 4 which may consist of ferrochromium. At 8 this tubule 4 has soldered to it in a vacuum tight manner, for example by means of copper, the centreing body 5 proper. The body 5 possesses a location lug 6 and a circular groove 1 which serves to hold the tube in the holder. Upon exhaustion the aperture in the body 5 may be closed by means of a plug 9. In order to increase the strength the body 5 may be slightly let in the bottom of the tube, as shown in the drawing, but it may also rest on the bottom surface of the plate.

In Fig. 2 the bulb of the tube is designated I0, the glass bottom plate i l. Into the bottom plate H are sealed the contact members l2 and the exhaust tube 13 Which entirely consists of ferrochromium. Similarly to the aforesaid case this exhaust tube is possessed of a location lug M, a groove l5 and is closed by means of a plug 16.

It will be obvious that also other embodiments of the invention are possible.

What I claim is.

1. An electric discharge tube base assembly comprising a glass base portion provided with a central aperture, an envelope portion hermetically sealed to the periphery of said base portion, a plurality of electric contact pin members concentric to said aperture and extending from the inner and outer sides of said base portion, and a metal member centrally positioned with. respect to said contact pins having a given portion thereof hermetically sealed to said base portion and an end portion thereof integrally united to said given portion and extending beyond the outer end of said contact pin members, said 2 metal member being provided with a central bore ccinciclent to the aperture of said base portion and open to the inner side of said base portion, and the end portion of said metal member con prising a member on the peripheral surface thereof and means to hermetically seal said central bore.

2. An electric discharge tube base assembly comprising a glass base portion provided with a central aperture, an envelope portion hermetically sealed to the periphery of said base portion, a plurality of electric contact pin members concentric to said aperture and extending from the inner and outer sides of said base portion, and a metal member centrally positioned with respect to said contact pins and having a given portion thereof hermetically sealed to said base portion and an end portion thereof integrally united to said given portion and extending beyond the outer end of said contact pin members, said r metal member being provided With a central bore coincident to the aperture of said base portion and open to the inner side of said base portion, the portion of said metal member sealed to said base portion having a temperature coefficient of expansion substantially equal to the temperature coeificient of expansion of said base portion, and the end portion of said metal member comprising a longitudinally extending location lug member on the peripheral surface thereof and means to hermetically seal said central bore.

longitudinally extending location lug :1

3. An electric discharge tube base assembly comprising a glass base portion provided with a central aperture, an envelope portion hermetically sealed to the periphery of said base portion, a plurality of electric contact pin members concentric to said aperture and extending from the inner and outer sides of said base portion, and a metal member centrally positioned with respect to said contact pins and comprising a ferrochromium portion hermetically sealed to said base portion and extending beyond the outer side of said base and an iron tubular portion integrally united and hermetically secured to the said extending ferrochromium portion and extending beyond the outer end of said contact pin members, said ferrochromium portion being provided with a central bore coincident to the aperture of said base portion and open to the inner side of said base portion, and the said iron tubular portion comprising a longitudinally extending location lug member on the peripheral surface thereof and means within said iron tubular portion hemetically sealing the bore thereof.

4. An electric discharge tube base assembly comprising a glass base portion provided with a central aperture, an envelope portion hermetically sealed to the periphery of said base portion, a plurality of electric contact pin members concentric to said aperture and extending from the inner and outer sides of said base portion, and a metal alloy member centrally positioned with respect to said contact pins and having a given portion thereof hermetically sealed to said base portion and an end portion thereof integrally united to said given portion and extending beyond the outer end of said contact pin members, said metal alloy member being provided with a central bore coincident to the aperture of said base portion and open to the inner side of said base portion and having a temperature coefiicient of expansion substantially equal to the temperature coefficient of expansion of said base portion, and the end portion of said metal alloy member comprising a longitudinally extending location lug member on the peripheral surface thereof and means Within said end portion hermetically sealing said central bore.

WILI-IELMUS ANTONIUS ROOVERS.

CKTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,044 Thomas Aug. 3, 1937 2,205,502 Tr-omp June 25, 1940 FOREIGN PATENTS Number Country Date 115,092 Australia May 1, 1941 

